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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education Ordinary Level * 3 5 3 9 3 7 7 5 9 2 * 5070/22 CHEMISTRY Paper 2 Theory October/November 2011 1 hour 30 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions. Write your answers in the spaces provided in the Question Paper. Section B Answer any three questions. Write your answers in the spaces provided in the Question Paper. A copy of the Periodic Table is printed on page 20. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A B6 B7 B8 B9 Total This document consists of 17 printed pages and 3 blank pages. DC (NF/CGW) 34310/2 © UCLES 2011 [Turn over 2 Section A For Examiner’s Use Answer all the questions in this section in the spaces provided. The total mark for this section is 45. A1 Choose from the following list of elements to answer the questions below. calcium chlorine hydrogen iodine nickel sodium vanadium zinc Each element can be used once, more than once, or not at all. Which element (a) forms an oxide which is amphoteric, ..................................................................................................................................... [1] (b) is a catalyst in the hydrogenation of alkenes, ..................................................................................................................................... [1] (c) oxidises aqueous bromide ions to bromine, ..................................................................................................................................... [1] (d) is used in water purification to kill bacteria, ..................................................................................................................................... [1] (e) is formed at the cathode when a dilute aqueous solution of sodium chloride is electrolysed, ..................................................................................................................................... [1] (f) can be used in the sacrificial protection of iron? ..................................................................................................................................... [1] [Total: 6] © UCLES 2011 5070/22/O/N/11 3 A2 Pure oxygen for industrial use is obtained from the air. (a) (i) For Examiner’s Use State the percentage by volume of oxygen in clean air. ............................................................................................................................. [1] (ii) Explain how fractional distillation is used to obtain oxygen from the air. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [2] (b) When acetylene, C2H2, burns in oxygen it produces a very hot flame. State one industrial use for this oxyacetylene flame. ..................................................................................................................................... [1] (c) Acetylene has a triple covalent bond between its carbon atoms. Draw a ‘dot-and-cross’ diagram for acetylene. You need only show the outer electrons. [1] © UCLES 2011 5070/22/O/N/11 [Turn over 4 (d) Oxygen reacts with magnesium to form magnesium oxide. Draw diagrams to show the complete electronic structure and charges of both ions present in magnesium oxide. [2] (e) Oxygen, O2, in the atmosphere can react to form ozone, O3. (i) Write an equation for this reaction. ............................................................................................................................. [1] (ii) In the upper atmosphere there is a layer of ozone surrounding the Earth. Explain the importance of this layer in terms of human health. .................................................................................................................................. ............................................................................................................................. [1] [Total: 9] © UCLES 2011 5070/22/O/N/11 For Examiner’s Use 5 A3 The alkanes are an homologous series of saturated hydrocarbons with the general formula CnH2n+2. For Examiner’s Use (a) What do you understand by the term hydrocarbon? ..................................................................................................................................... [1] (b) Write the molecular formula for the alkane containing seven carbon atoms. ..................................................................................................................................... [1] (c) Two different structural formulae can be written for the alkane having the molecular formula C4H10. H H H H H H C C C C H H H H H H butane H H C H H C C C H H H H methylpropane What term is given to compounds with the same molecular formula but different structural formulae? ..................................................................................................................................... [1] (d) A student ignites a mixture of 15 cm3 of propane and 100 cm3 of oxygen. The oxygen is in excess. All measurements of volume are taken at room temperature and pressure. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) Calculate the volume of carbon dioxide formed, .............................................................................................................................. cm3 [1] the volume of unreacted oxygen remaining. ...............................................................................................................................cm3 [1] (e) Explain why the incomplete combustion of an alkane in an enclosed space is hazardous. .......................................................................................................................................... ..................................................................................................................................... [2] [Total: 7] © UCLES 2011 5070/22/O/N/11 [Turn over 6 A4 Coal is largely carbon. For Examiner’s Use (a) Carbon burns in excess air to form carbon dioxide. C(s) (i) + O2(g) CO2(g) ΔH = –393.5 kJ / mol Draw an energy profile diagram for this reaction on the axes below. On your diagram label • • • the reactants and products the enthalpy change for the reaction the activation energy enthalpy reaction pathway [3] (ii) Give a test for carbon dioxide. test ........................................................................................................................... observation .......................................................................................................... [2] © UCLES 2011 5070/22/O/N/11 7 (b) Coal contains a small amount of sulfur. (i) For Examiner’s Use Explain how the burning of coal results in the formation of acid rain. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [3] (ii) State one effect of acid rain. ............................................................................................................................. [1] (c) Oxides of nitrogen also contribute to acid rain. They can be formed naturally in the atmosphere from nitrogen and oxygen. (i) What condition is needed to allow nitrogen and oxygen to combine in the atmosphere? ............................................................................................................................. [1] (ii) Nitric acid in the atmosphere can chemically erode buildings made from carbonate rocks. Write an equation for the reaction of nitric acid, HNO3, with calcium carbonate, CaCO3. [2] [Total: 12] © UCLES 2011 5070/22/O/N/11 [Turn over 8 A5 Bromine is a halogen. It has two naturally-occurring isotopes. For Examiner’s Use (a) Define the term isotopes. .......................................................................................................................................... ..................................................................................................................................... [1] (b) One isotope of bromine has the symbol 81Br. 35 State the number of protons, neutrons and electrons in this isotope of bromine. protons ............................ neutrons .......................... electrons ......................... [2] (c) Bromine is a liquid at room temperature. (i) Draw a diagram to show the arrangement of the molecules in liquid bromine. Show a bromine molecule as z . [2] (ii) A small amount of liquid bromine was placed in the bottom of a sealed flask. After thirty minutes the brown colour of the bromine had spread throughout the flask. air liquid bromine start after 30 minutes Use the kinetic particle theory to explain these observations. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [3] © UCLES 2011 5070/22/O/N/11 9 (d) Bromine forms a variety of compounds with other halogens. (i) For Examiner’s Use Bromine reacts with fluorine to form bromine(I) fluoride, BrF. Write an equation for this reaction. ............................................................................................................................. [1] (ii) Another compound of bromine and fluorine is bromine(V) fluoride, BrF5. Calculate the percentage of bromine by mass in bromine(V) fluoride. [2] [Total: 11] © UCLES 2011 5070/22/O/N/11 [Turn over 10 Section B For Examiner’s Use Answer three questions from this section in the spaces provided. The total mark for this section is 30. B6 Ammonia is made by the Haber process. (a) (i) Write an equation for the formation of ammonia in the Haber process. ............................................................................................................................. [1] (ii) State the essential conditions for the Haber process. .................................................................................................................................. ............................................................................................................................. [3] (b) Ammonia is used to make fertilisers. Explain why farmers use fertilisers. .......................................................................................................................................... ..................................................................................................................................... [1] (c) Many fertilisers are ammonium salts. Explain why adding calcium hydroxide to the soil can cause the loss of nitrogen from the ammonium salts added as fertilisers. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (d) Fertilisers such as ammonium nitrate and ammonium phosphate are solids. They can get into lakes and cause excessive growth of algae. (i) Explain how these fertilisers get into lakes. .................................................................................................................................. ............................................................................................................................. [2] (ii) What name is given to the enrichment of lakes with nitrates and phosphates which leads to the death of plant and animal life in the lakes? ............................................................................................................................. [1] [Total: 10] © UCLES 2011 5070/22/O/N/11 11 B7 Sulfuric acid is a strong acid. Ethanoic acid is a weak acid. For Examiner’s Use (a) What do you understand by the terms strong acid and weak acid ? .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [1] (b) Compare and explain the difference in the electrical conductivity between a strong and a weak acid. ..................................................................................................................................... [1] (c) A dilute solution of sulfuric acid contains hydrogen ions, hydroxide ions and sulfate ions. When this solution is electrolysed, hydrogen gas is formed at the cathode and oxygen gas is formed at the anode. (i) Explain why hydrogen is formed at the cathode. .................................................................................................................................. ............................................................................................................................. [1] (ii) Write the ionic equation for the reaction at the anode. ............................................................................................................................. [2] © UCLES 2011 5070/22/O/N/11 [Turn over 12 (d) Magnesium reacts with dilute sulfuric acid. Mg(s) (i) + H2SO4(aq) MgSO4(aq) + For Examiner’s Use H2(g) Describe how you can follow the progress of this reaction. What measurements can you use to calculate the speed of the reaction? .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [3] (ii) A student reacts 3.0 g of magnesium with 2.5 mol / dm3 sulfuric acid. Calculate the minimum volume of sulfuric acid that reacts with all the magnesium. [2] [Total: 10] © UCLES 2011 5070/22/O/N/11 13 B8 The table gives some information about the first five members of the carboxylic acid homologous series. carboxylic acid formula boiling point / °C HCO2H 101 ethanoic acid CH3CO2H 118 propanoic acid C2H5CO2H 141 methanoic acid butanoic acid pentanoic acid (a) (i) For Examiner’s Use 166 C4H9CO2H Estimate the boiling point of pentanoic acid. ............................................................................................................................. [1] (ii) Draw the structure of butanoic acid. Show all atoms and bonds. [1] (iii) Ethanoic acid reacts with sodium. Write an equation for this reaction. ............................................................................................................................. [1] © UCLES 2011 5070/22/O/N/11 [Turn over 14 (b) Carboxylic acids react with alcohols to form esters. (i) For Examiner’s Use Name the ester formed when ethanoic acid reacts with ethanol. ............................................................................................................................. [1] (ii) The diagram shows the repeat unit of poly(ethenyl ethanoate) CH3CO H O C C H H n Draw the structure of the monomer used to make poly(ethenyl ethanoate). [1] © UCLES 2011 5070/22/O/N/11 15 (c) Carboxylic acid X contains 55.8% carbon, 7.0% hydrogen and 37.2% oxygen. (i) For Examiner’s Use Calculate the empirical formula of X. [2] (ii) A molecule of carboxylic acid X contains four carbon atoms. What is its molecular formula? ............................................................................................................................. [1] (iii) Carboxylic acid X is an unsaturated compound. Give a test for an unsaturated compound. test ........................................................................................................................... observation .......................................................................................................... [2] [Total: 10] © UCLES 2011 5070/22/O/N/11 [Turn over 16 B9 Barium is a reactive metal in Group II of the Periodic Table. Barium reacts with water in a similar way to sodium. The products of the reaction are aqueous barium hydroxide and a colourless gas. (a) (i) Write an equation, including state symbols, for this reaction. ............................................................................................................................. [3] (ii) Aqueous barium hydroxide is neutralised by hydrochloric acid. Write the simplest ionic equation for this reaction. ............................................................................................................................. [1] (b) Explain why barium metal conducts electricity. ..................................................................................................................................... [1] (c) Barium oxide reacts with aluminium. 3BaO + 2Al 3Ba + Al2O3 Explain how this equation shows that aluminium is a reducing agent. .......................................................................................................................................... ..................................................................................................................................... [1] (d) Barium sulfate is an insoluble compound. Describe how a pure dry sample of barium sulfate is prepared from aqueous barium nitrate. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [4] [Total:10] © UCLES 2011 5070/22/O/N/11 For Examiner’s Use 17 BLANK PAGE © UCLES 2011 5070/22/O/N/11 18 BLANK PAGE © UCLES 2011 5070/22/O/N/11 19 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2011 5070/22/O/N/11 © UCLES 2011 20 Calcium 5070/22/O/N/11 Strontium Radium 45 89 89 227 Actinium Ac † Key b X a b = atomic (proton) number X = atomic symbol a = relative atomic mass 72 Hafnium * Lanthanum 57 178 Hf 40 Zirconium Zr 91 Titanium 139 Yttrium Y 22 48 Ti La 39 21 Scandium Sc * 58–71 Lanthanoid series † 90–103 Actinoid series 88 Francium 87 226 Ra 223 Barium 56 Caesium Fr 55 137 Ba 133 Cs 38 Rubidium 37 88 Sr 85 Rb 19 Potassium 40 Ca 39 Magnesium Sodium 12 24 Mg 23 Na Beryllium 4 Lithium K 11 3 9 Be 7 II Li I 51 93 Ta 181 Niobium Nb 90 58 73 52 96 Mo W 184 55 Tc 186 Re 144 Nd 92 60 Uranium U 238 Neodymium 75 Rhenium 43 Technetium 25 Manganese Mn 27 59 28 59 29 64 30 65 5 Ru 101 Iron 190 Pm 147 Osmium Os 237 Np 93 Neptunium 61 Promethium 76 44 Ruthenium 26 56 Fe Sm 150 Iridium 244 Pu 94 Plutonium 62 Eu 152 Platinum 243 Am 95 Americium 63 Europium 78 195 Pt Ir 46 Palladium Pd 106 Nickel Ni 192 Samarium 77 45 Rhodium Rh 103 Cobalt Co Gd 157 Gold Au 197 Silver 96 64 Curium Cm 247 Gadolinium 79 47 Ag 108 Copper Cu 201 Bk 247 Terbium Tb 159 Mercury Hg 97 Berkelium 65 80 48 Cadmium Cd 112 Zinc Zn 11 6 Dy 162 Thallium Tl 204 Indium 251 Cf 98 Californium 66 Es 252 Holmium Ho 165 Lead Pb 207 Tin 99 Einsteinium 67 82 50 119 Sn 115 32 Germanium Ge 73 Silicon In Gallium Dysprosium 81 49 31 70 Ga 14 28 Si Carbon 27 Aluminium 13 12 C Al Boron B 7 14 75 Sb 122 Arsenic As Bi 209 Fermium Fm 257 Erbium Er 167 Bismuth 100 68 83 51 Antimony 33 15 Phosphorus P 31 Nitrogen N 8 Se 79 Sulfur S 32 Oxygen 209 Po 169 Md 258 Thulium Tm 101 Mendelevium 69 84 Polonium 52 Tellurium Te 128 Selenium 34 16 16 O 9 Yb 173 Astatine At 210 Iodine I 127 Bromine Br 80 Chlorine 259 No 102 Nobelium 70 Ytterbium 85 53 35 17 Cl 35.5 Fluorine F 19 Lr 260 Lutetium Lu 175 Radon Rn 222 Xenon Xe 131 Krypton Kr 84 Argon Ar 40 Neon 103 Lawrencium 71 86 54 36 18 10 Ne 20 Helium 2 0 Hydrogen VII 4 VI He V 1 IV H III The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). 91 Protactinium Thorium 231 Pa Th 232 Praseodymium Cerium 59 141 Pr 140 74 Tungsten 42 Molybdenum 24 Chromium Cr Ce Tantalum 41 23 Vanadium V 1 Group DATA SHEET The Periodic Table of the Elements 20
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